Grand Teton National Park rangers on Thursday recovered the body of a 21-year-old Iowa climber who was knocked off the 13,770-foot-high Grand Teton during a lightning storm that injured 16 other mountaineers the day before.

Park officials identified the victim as Brandon Oldenkamp, 21, of Sanborn, Iowa. Oldenkamp was in a climbing harness, tied to a rope and on belay when the lightning struck, park spokeswoman Jackie Skaggs said. His friends watched him disappear at a feature known as the Belly Roll on the Owen-Spalding route.

Rangers found his body about 2,000 feet down in Valhalla Canyon below the Black Ice Couloir.

Park officials are still investigating the cause of death, unsure if it was a lightning strike or the fall. How or why his safety system failed is not yet understood, but a bolt of lightning may have severed the rope, Skaggs said.

The storm prompted what is likely the most complex rescue in park history involving 83 persons who worked to bring 16 injured climbers off the peak before nightfall. The intense and enduring storm struck about midday, and the rescued climbers told a doctor they had been hit several times by lightning.

Steve Tyler and Henry Appleton, employees at Signal Mountain Lodge in the park, were two of the climbers on the mountain, along with Andrew Larsen, 23, from Bozeman, Montana. Names of other members of what was three parties were not available late Thursday.

Exum Mountain Guides employee Dan Corn was just leaving the 11,650-foot Lower Saddle when he got a text message that something was amiss. Six Exum parties, including 13 clients, had already reached the summit and were descending below the Lower Saddle.

Corn guided the first rescue helicopter to its landing at the saddle and then started up the Owen-Spalding route with two Jenny Lake climbing rangers.

They first encountered two men who were descending and looking for help. They then found another few who had lost their way down and anchored them in place.

The next victim was at the bottom of the Owen Chimney – at about 13,200 feet and where the climbing is serious and exposed. He was conscious but hypothermic and had lost feeling in his legs, Corn said.

They anchored him and climbed higher. They found three more climbers at the top of the chimney, conscious, but in shock, Corn said.

“It was like they were alert and oriented, but not fully there,” he said. Corn saw a variety of injuries.

“There were full burns and exit wounds” from lightning, he said. Despite the carnage and multiple injuries, the guide and rangers kept their heads.

“You go up and do the best you can,” Corn said.

More rangers began catching up to find and treat climbers yet higher on the peak.

Jenny Lake climbing ranger Jim Springer, who organized the rescue from the Lupine Meadows rescue cache on the valley floor, said he was nearly overwhelmed when he learned that 17 climbers were in distress.

“I had to basically stop and take a deep breath,” he said at the cache and command center where he was still working Thursday. At the time the full extent of the damage became apparent, Springer had already summoned all available resources.

“There was nobody else to call,” Springer said. “There were people all over the mountain.”

Nevertheless, rangers were business-like, Springer said.

“It wasn’t chaotic,” he said. “It went very smoothly.”

Rangers would say “I have a 38-year-old male with this, this and this,” Springer said of the radio conversations with crews. “It went on and on.”

Of five climbers admitted to St. John’s Hospital on Wednesday, three remained there Thursday in good condition in the primary care unit, a hospital spokeswoman said. One other climber was taken to a hospital in Idaho Falls after the incident.